HVAC heating systems typically include a combustion chamber that works cooperatively with a burner. The burner receives fuel from a fuel source, and when ignited, provides the necessary heat to a controlled space. Gases from the combustion chamber typically exit the combustion chamber and the controlled space through a flue.
A problem recognized with some HVAC systems is that if the flue becomes sufficiently blocked or otherwise obstructed, gasses generated in the combustion chamber may fail to exit the chamber and thus the controlled space. Such gasses can back up into a house or building, creating hazardous conditions for occupants. A flue can become blocked for any number of reasons, including nesting animals, fallen sticks/leaves, ice blockages, and/or other objects or materials that may become lodged in the flue. In some cases, the flue may become sufficiently blocked by simply by build up of ash, creosote and/or other combustion waste vented from the chamber.
To help detect such flue blockages, pressure sensors, flow sensors, temperature sensors, and the like, are often provided in the flue to detect insufficient flow of exhaust gases through the flue. However, it has been found that these additional sensor elements, wiring, and connections can unduly increase the cost and possibly reduce the reliability of the HVAC system.